This project will explore how climate regulates variability in tree seed production, and predict future changes in tree reproduction and its consequences on ecosystem dynamics.
Many tree species show a reproductive strategy known as masting, which is characterised by switching between years of bumper investment in reproduction (“mast years”), and years of low or no investment in fruit and seeds. Remarkably, this variation is synchronised within and across tree populations. Various mechanisms may explain how trees are able to a) vary their seed production year-to-year, and b) synchronise this variation between individuals (Pearse et al. 2016). Most of these mechanisms rely either directly or indirectly on climate as the key regulator of masting, implying that masting may respond to changes in climate. Recent studies have reported global changes in masting patterns over the last century (Pearse et al., 2017), but the response of masting to climate change remains highly uncertain (e.g. Kelly et al., 2013 and responses to this paper).
Changes to masting patterns are of fundamental importance to the functioning and dynamics of forest ecosystems (Vacchiano et al., 2018). For example, mast years act as resource pulse in ecosystems, leading to cascading effects on the population dynamics of seed-eating mammals, and subsequently predators and parasites (Figure 1). These dynamics can, to take one example, result in spikes in the rate of human infection by tick-borne diseases including Lyme, which have been shown to occur two years after major masting events.
Environmental challenge: Changes in the variability of seed production in masting species will have widespread impacts on tree-based ecosystems, and wider impacts including on human health. How will masting respond to climatic and environmental change?
The objective of this project is to evaluate the response of masting to recent changes in climate, and predict future changes in masting resulting from ongoing environmental change. Until now, this has been challenging due to the paucity of long masting time-series. However, we now have the opportunity robustly test this using the MASTREE+ database, currently in development as part of the MAST-NET project: (www.liverpool.ac.uk/geography-and-planning/research/mast-net). The candidate will have the first opportunity to explore the potential of this global-scale masting dataset, leading on the analysis of global-scale masting patterns and their responses to climate change. Depending on the interests of the successful applicant, further opportunities exist to utilise this dataset to explore, for example, geographical variation in masting, differences in response between species/genera, and variation across environmental gradients.
The candidate will be will integrated into the MAST-NET project, providing many opportunities for collaboration with institutions in North America, Europe and Japan. This includes the opportunity for experiments and fieldwork in Europe and North America to investigate the mechanisms that regulate masting. For example, this may include using radiocarbon measurements to determine the role of stored reserves in masting, and how this varies between years and species (working with Dr. Josh Dean). It will also involve the development of models to evaluate the likely response of masting to climate change. A key challenge will be establishing how future responses will vary between species based on the species-specific mechanisms that have evolved to regulate seed crops (variability and synchrony) (Bogdziewicz et al. 2017).
Interested candidates are strongly encouraged to contact the lead supervisor for more information.
To apply for this opportunity, please visit: https://www.liverpool.ac.uk/study/postgraduate-research/how-to-apply/
and click the ’Apply online’ button.
Pearse, Koenig & Kelly. (2016). Mechanisms of mast seeding: resources, weather, cues, and selection, New Phytologist, 212, 546-562
Bogdziewicz et al. (2017). Masting in wind-pollinated trees: system-specific roles of weather and pollination dynamics in driving seed production. Ecology, 98, 2615-2625
Hacket-Pain et al. (2018). Climatically controlled reproduction drives interannual growth variability in a temperate tree species. Ecology Letters, 21, 1833-1844
Vacchiano, Ascoli … Hacket-Pain. 2018. Reproducing reproduction: How to simulate mast seeding in forest models. Ecological modelling, 376, 40-53
Ascoli, Maringer, Hacket-Pain et al. (2017a). Two centuries of masting data for European beech and Norway spruce across the European continent. Ecology, 98, 1473
Ostfeld RS, et al. 2018. Tick-borne disease risk in a forest food web. Ecology. 99,1562-1573.